1. Field of the Invention
The present invention relates to a novel deinking agent for regeneration of waste paper to prepare regenerated pulp and to a floatation method employing it.
2. Description of the Prior Art
The floatation method is a known method of deinking for regeneration of waste paper. In the floatation method, waste paper is disaggregated by a pulper and the like and then deinking is effected with a deinking agent in combination with an alkali and a bleaching agent. Ink in the waste paper is separated from the pulp fibers to form aggregates. Air is blown into the pulp slurry thus formed to make foams. The ink which adheres to the foams is removed with the foams from the pulp slurry.
In the floatation method, various kinds of surface active agents have been utilized as the deinking agent. Soaps of higher fatty acids have long been the most popular agents. This kind of deinking agent has an excellent ability to form ink aggregates. However, adhesion of the ink to the apparatus occurs when this kind of deinking agent is utilized. Also, because the ability of this kind of deinking agent to make foams is not sufficient, the ink which is aggregated and floating cannot be removed completely with the foams. Thus, the ink occasionally remains in the pulp. Because their ability to make foams is insufficient, other foaming agents are generally utilized in combination with this kind of deinking agent.
Deinking agents other than soaps of higher fatty acids, such as anionic surface active agents, e.g., salts of alkylbenzenesulfonic acids, salts of higher alcohol sulfuric acid esters, salts of .alpha.-olefin sulfonic acids, dialkyl sulfosuccinates and the like and nonionic surface active agents like ethylene oxide adducts of alkylphenols, higher alcohols and fatty acids, alkanolamines and the like have been utilized recently. However, these deinking agents do not have sufficient ability to aggregate and remove ink in the floatation method. The problem of the insufficient ability of fatty acid soaps to make foams has been solved to some extent but a problem still remains, viz., foams made in the floatation method persist even after the period in which the foams are necessary has ended. Thus, the ink aggregated and adhered to the foams remains in the floatator longer than necessary. This situation occasionally causes the problem of ink spots.
When pulp regenerated by a floatation-type process is utilized, the so-called pitch trouble occurs rather frequently in the paper making process. This situation causes another problem, viz., agents such as pitch controlling agents must be added in larger amounts.
Japanese Patent Tokukai Sho 61-89394 teaches the use of a deinking composition for a flotation process comprising a polyoxyethylene oxide adduct of a higher fatty acid monoethanolamide. The English abstract of this publication identifies the surfactant component of the ink-removing composition as a polyethylene oxide adduct of a higher fatty acid monoethanolamide of the formula EQU R.sub.1 --CON[(CH.sub.2 CH.sub.2 O).sub.p H][(CH.sub.2 CH.sub.2 O).sub.q H].
In contradistinction, applicants employ as the surfactant an alkylene oxide(s) adduct of the mixture of reaction products obtained by the reaction of a natural oil or fat with an alkanolamine, which mixture of reaction products is a mixture of: ##STR1## where
R means alkyl group of C.sub.7 -C.sub.23,
AO means alkylene oxide of C.sub.2 -C.sub.6,
X.sub.1, X.sub.2 means acyl group of C.sub.8 -C.sub.24 or H,
m.sub.1, M.sub.2 means 1-200,
and ##STR2## where
AO means alkylene oxide of C.sub.2 -C.sub.6,
X.sub.3, X.sub.4, X.sub.5 means acyl group of C.sub.8 -C.sub.24 or H,
n.sub.1, n.sub.2, n.sub.3 means 0-300.
This adduct of a mixture of reaction products performs as a deinking agent in a superior manner to the ethylene oxide adducts of the amides of JP Tokukai Sho 61-89394.